Paul McCartney and U2's Bono fired up a huge London crowd with Sergeant Pepper's Lonely Hearts Club Bandtoday for the anti-poverty crusade, Live 8, the biggest music event ever staged.
Starting the show with the familiar lyrics: "It was 20 years ago today," ex-Beatle McCartney harked straight back to the 1985 Live Aid concerts.
Bono performs at the Live 8 concert in Hyde Park in London today.
Back then, a new standard in fund-raising was achieved by organiser Bob Geldof to help the victims of Ethiopia's famine.
This time, rocker Geldof wants up to a million people to attend 10 shows across four continents to pressure world leaders meeting next week to do more to end extreme poverty.
“Mahatma Gandhi freed a continent, Martin Luther King freed a people, Nelson Mandela freed a country. It does work -- they will listen,” he told some 200,000 people in London's Hyde Park.
Bono, another key celebrity campaigner, summed up the message: “We're not asking you to put your hand in your pockets but we are asking people to put their fist in the air.“
Chariman of Microsoft, Bill Gates, addressed the crowd saying: "The generosity we are asking for can save millions of lives. Some day in the future all people, no matter where they are born, will be able to lead a healthy life.
"We can do this and when we do it will be the best thing that humanity has ever done." he added.
Leaders of the Group of Eight industrialised nations meet near Edinburgh on July 6-8, and British Prime Minister Tony Blair has Africa and poverty high on the agenda.
In Edinburgh itself, tens of thousands of demonstrators wearing white marched through the city on Saturday as part of the related Make Poverty History campaign.
Tokyo kicked off Live 8 earlier in the day, with Icelandic star Bjork helping fill a 10,000-capacity venue at short notice.
The diminutive star expressed the sense of helplessness she felt in the face of Africa's extreme poverty.
“I look at the news, I see people starving, I am crying. I'm a total mess,” she told reporters afterwards.
“You try to think how you're going to break through this cobweb of problems and bureaucracy and how on Earth anybody is going to make any change.“
Live 8 was also under way in Rome and in Berlin, where up to 100,000 people gathered around the Brandenburg Gate. But in Johannesburg a crowd of only 3-4,000 had shown up early on, well short of the 40,000 organisers had expected.